Smithsonite

(Bonamite)
Chemistry: Zinc carbonate
Crystal system: Trigonal; mostly massive and stalactitic, botryoidal, granular or as encrustations; rare rhombohedral crystals are known.
Color: Translucent to opaque; light green, blue, pink, yellow, purple, rarely colorless.
Hardness: 4.5 - 5
Cleavage: Perfect: in rhombohedral; fracture: brittle, uneven.
Specific gravity: 4.3 – 4.5
Refractive index: 1.621 – 1.849; Uniaxial negative; 0.228; 1.72 mean.
Luster: Pearly-dull; rarely vitreous
Dispersion: High
Dichroism: -
Occurrence: As a secondary mineral in oxidized zone ore deposits; Greece, Mexico, USA, Spain, Namibia.

Notes
Softness makes it unsuitable for jewelry; faceted stones are collectors items; carbonate will efferverse with acid; may look like chrysoprase or turquoise; alternate name bonamite derived from name of New York jeweler who first marketed smithsonite jewelry; faceted, cabochon.